title: Cinchona alkaloid catalyzed enantioselective amination of α,β-unsaturated ketones: an asymmetric approach to Δ2-pyrazolines.
abstract: Δ2-Pyrazolines are of significant medicinal and synthetic interest due to their therapeutic properties and utility in the synthesis of 1,3-diamines, yet few asymmetric methods exist to prepare them. An unprecedented highly enantioselective organocatalytic synthesis of 2-pyrazolines was achieved through an asymmetric conjugate addition catalyzed by 9-epi-amino cinchona alkaloids followed by deprotection-cyclization, which furnished chiral 2-pyrazolines in 46-78% yield and 59-91% ee. This bifunctional catalytic methodology thus provides easy access to considerable range of optically active 3,5-dialkyl 2-pyrazolines.
authors.affiliation: Department of Chemistry, Brandeis University, 415 South St., Waltham, MA 02454-9110, USA.
authors.forename: Nathaniel R
authors.initials: NR
authors.lastname: Campbell
authors.forename: Bingfeng
authors.initials: B
authors.lastname: Sun
authors.forename: Ravi P
authors.initials: RP
authors.lastname: Singh
authors.forename: Li
authors.initials: L
authors.lastname: Deng
keywords: asymmetric catalysis; cinchona alkaloids; conjugate addition reaction; cyclization; enones; Δ2-Pyrazolines